1. Field of the Invention
The present invention relates to a master cylinder for braking and a motorcycle on which the master cylinder for braking is mounted. In particular, the present invention relates to a master cylinder for braking in which a sub-tank for supplying working oil for braking is integrally provided on a master cylinder main body, and which is disposed with its major axis directed substantially in the vertical direction, and a motorcycle on which the master cylinder for braking is mounted.
2. Background Art
A master cylinder is known as a means for generating hydraulic pressure to be applied to a front brake. Conventional master cylinders are configured with a sub-tank for supplying working oil for braking provided on a master cylinder main body, with the major axis of the master cylinder main body being substantially parallel to the ground. A master cylinder of this type is disclosed in Japanese Utility Model Laid-open No Hei 3-2962, and Japanese Patent Laid-open No. Hei 10-236374.
In this type of master cylinder, a plurality of ports in a partition wall which partitions the sub-tank from the master cylinder main body are formed using a tool passing through the working oil supply port. A lid for blocking the working oil supply port is provided substantially in parallel to the major axis of the master cylinder main body
Taking into account the supply of working oil upon maintenance, the lid must be disposed substantially in parallel to the round, and therefore, the major axis ot the master cylinder main body must be substantially parallel to the ground. In this case, it is difficult to ensure a space for disposing and mounting the master cylinder in a finished vehicle.
If the major axis of the master cylinder for braking is arranged substantially perpendicular to the ground to ensure mounting space for the master cylinder, a sub-tank for supplying working oil for braking must be provided separately from the master cylinder main body. In addition, a rubber brake hose is required to connect the sub-tank to the master cylinder main body. This configuration is shown in Japanese Patent Laid-open No. Sho 63-258285.
However, it is difficult to ensure a space for mounting the separate sub-tank and a space for allowing the brake hose to pass therethrough Further, since the sub-tank and the brake hose must be fixed by stays and bolts, the number of parts is increased.
An object of the present invention is to solve the above-described problems in conventional master cylinders for braking, and to provide a master cylinder for braking in which a sub-tank for supplying working oil for braking is integrally provided on a master cylinder main body.
It is an additional object of the invention to provide a master cylinder of reduced size which is disposed so that its major axis extends substantially in the vertical direction.
It is a further object of the present invention to provide a master cylinder of simplified structure which reduces space used in a motorcycle, allowing for a narrower motorcycle body.
It is still a further object of the present invention to provide a motorcycle on which a master cylinder having the above-mentioned characteristics is mounted
To achieve the above objects and other advantages, a master cylinder for braking is provided with a master cylinder main body and a sub-tank for supplying working oil for braking. The sub-tank is integrated with the master cylinder main body, and has an elongated shape. The sub-tank""s major axis is substantially parallel to the major axis of the master cylinder main body.
The master cylinder in which the sub-tank for supplying working oil for braking is integrally provided on the master cylinder main body is formed therefore has an elongated shape. As a result, the master cylinder for braking has a reduced width This makes it possible to simplify the structure of the master cylinder to slim the appearance of the master cylinder, and to save space in the brake system.
A mounting seat for mounting a brake hose is formed at one end in the major axis direction of the master cylinder main body so as to extend perpendicularly to the major axis of the master cylinder main body. A mounting portion of the brake hose is fastened to the mounting seat, and one end of the sub-tank extends upwardly from the mounting seat of the brake hose, and has a port for supplying working oil for braking.
As a result, the structure of the connecting portion of the brake hose to the master cylinder main body is reduced in size and simplified. Further, since the brake hose is rotatable around the major axis of the master cylinder main body, the degree of freedom in layout of the other peripheral parts can be improved. For example, upon supply of working oil for braking, the mounting portion of the brake hose does not obstruct maintenance work.
The inner side of the sub-tank has a cylindrical shape, and a bag-like diaphragm and an oil separator are disposed in the sub-tank. The inside of the diaphragm communicates with atmospheric air for expansion and contraction
As a result, upon initial braking operation of the disk type brake system, a part of the working oil is pressed back in the sub-tank. The pressing action due to the working oil thus pressed back is absorbed by contraction of the diaphragm, so that the initial braking operation of the brake system can be moderated. This prevents sudden braking and adds to the safety of the brake system.
Further, during running of the vehicle, the working oil in the sub-tank intakes air due to vibration and bubbles These bubbles entrapped in the working oil are separated from and blocked by the oil separator.
As a result, the bubbles in the working oil do not enter the cylinder chamber of the master cylinder. This improves the reliability of the master cylinder
The oil separator is integrally provided on the diaphragm, and is easily mounted, reducing the number of parts.
The master cylinder for braking is disposed on a side of a vehicle body so that the major axis of the master cylinder main body extends substantially in the vertical direction of the vehicle body.
As a result, the length of the vehicle body can be shortened. Even if an external force is applied to the master cylinder due to upsetting or the like, the moment applied to the mounting portion of the master cylinder can be reduced. This makes it possible to reduce the weight of the stays, etc. at the mounting portion of the master cylinder. Further, since the master cylinder does not have a large width, the motorcycle appears slim.
The master cylinder for braking is disposed so that the major axis of the sub-tank is positioned outwardly from the major axis of the master cylinder.
As a result, if the master cylinder for braking is used as the master cylinder for operating the rear brake, the width of the swing arm can be made wider toward the rear side of the vehicle body, so that a wide tire can be mounted without widening the pivot width. The pivot width is the transverse distance of the portion at which the right and left pivot plates are disposed.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.